1. Field of the Invention
The present invention relates to a cavity plate of an ink-jet printhead of an ink-jet printer, and further relates to the manufacturing process of the cavity plate.
2. Description of Related Arts
A conventional ink-jet printhead of an ink-jet printer is formed of a cavity plate that includes ink chambers, which are divided by separation walls, and a piezoelectric element attached to the cavity plate. In such an ink-jet printhead, a pressure change is caused within the ink chambers by the piezoelectric element, and which forces the ejection of ink through nozzles provided on the cavity plate.
Various manufacturing processes have been applied to produce the cavity plate. For example, the cavity plate can be made of ceramics or resin by injection molding, wherein the ink chambers and an ink reservoir are integrally molded. Also, the cavity plate can be made of photosensitive glass, on which the ink chambers and the ink reservoir are formed by an etching process.
However, many problems arise from the aforementioned conventional manufacturing process of the cavity plate. These problems are discussed below.
In injection molding of ceramics or resin, it is necessary to produce the mold for molding the cavity plate on which the ink chambers are aligned at minute intervals. This complicated arrangement causes the mold to be time-consuming and expensive to manufacture, and at the same time, difficult to modify the cavity plate immediately as necessity requires. Further, the materials (such as ceramics and resin) are necessarily sintered after injection molding, whereupon the materials shrink during the sintering process. This shrinkage has been a problem in manufacturing the cavity plate accurately due to the difficulty in its control.
In the etching process of photosensitive glass, it is difficult to control the depth of the ink chambers and the ink reservoir. Thus, the ink chambers and the ink reservoir cannot be formed with high precision.
It is therefore an object of the present invention to solve the problems described above.
Specifically, one aspect of the invention is of a cavity plate for an ink ejecting device, comprising multiple nozzles that eject ink, ink chambers arranged at regular intervals and connected to the nozzles, and an ink reservoir connected to all the ink chambers. The ink ejecting device having such a cavity plate ejects ink from the ink chambers through the nozzles, based on a pressure change caused within the ink chambers by a piezoelectric element.
According to the present invention, the cavity plate can be made of a plate-shaped base material having the ink reservoir thereon, and a chamber sheet pierced to form an ink channel array constituting the ink chambers and attached to the base material.
With this arrangement, the channel and the surface of the base material attached to the chamber sheet form the ink chamber as the circumferential wall and the base. The depth of the ink chambers is determined by the thickness of the chamber sheet, regardless of the accuracy in creating the ink channels. Such channels can be created by, for example, an electric discharge machine, etching process, or press working, without the necessity of the sintering process. This makes it possible to form accurate breadth of the ink chamber as well as accurate spacing width between the adjacent ink chambers. In this way, the ink chambers can be formed so precisely that uniform ink ejection performance is obtained.
Further, a nozzle sheet comprising the nozzles thereon is bonded to the front edge of the chamber sheet. The nozzles are connected to the ink chambers with opening portions provided at the tip of the ink channels. Alternatively, the nozzles may be formed directly on the front edge of the chamber sheet without the use of the nozzle sheet. In this case, the nozzles are connected to the ink chambers with connecting holes provided through the front edge portion of the chamber sheet. With these arrangements, the ink chambers are easily and certainly connected to the nozzles, and which results in good ink ejecting performance.
The chamber sheet and the base material have a similar coefficient of thermal expansion. Even if using hot-melt ink; which melts at a high temperature, the adhesive strength between the chamber sheet and the base material is maintained without warping when subjected to heat. It is therefore possible to prevent pressure leakage from the ink chambers, and thereby possible to eject ink appropriately.
The base material is much thicker than the chamber sheet, whereby the ink reservoir has a much larger capacity than the ink chamber. In this configuration, the ink reservoir certainly absorbs the pressure in the direction toward the ink reservoir, when applying a pressure to ink within the ink chambers. This reduces crosstalk between the adjacent ink chambers. At the same time, the base material has a high rigidity due to its thickness, and prevents pressure leakage in order to eject ink efficiently.
Another aspect of the invention is of the manufacturing process of the aforementioned cavity plate which does not increase production cost. This manufacturing process includes the steps of: forming the ink channel array constituting the ink chambers through the chamber sheet; forming the ink reservoir on the base material; bonding the chamber sheet and the base material; and connecting the ink chamber and the nozzle.
In the step of forming the ink channel array, for example, an electric discharge machine, etching process, or press working can be applied, without the necessity of a mold for injection molding. Thus, it is possible to reduce the production cost significantly, and at the same time, possible to modify the cavity plate immediately as necessity requires. Additionally, multiple chamber sheets that are laid one upon another can be processed simultaneously, which leads to the reduction in the production cost by sheet and the improvement of manufacturing efficiency.
In the step of connecting the ink chamber and the nozzle, the front edge portion of the chamber sheet is cut off after bonding the chamber sheet and the base material in order to provide opening portions at the tip of the channels. Since the opening portions are not formed at the time when the ink channel array is formed, the front edge portion of the chamber sheet is still sheet-shaped. Such a chamber sheet is easy to bond to the base material. Further, being reinforced with the base material, the front edge portion of the chamber sheet is easily cut off after the bonding without distorting the ink channels.
The opening portions are thus formed accurately at tip of the ink channels so that the ink chambers are certainly connected to the nozzles. Alternatively, the nozzle may be created directly on the front edge of the chamber sheet. At the same time, connecting holes are formed between the nozzles and the ink chambers through the front edge portion of the chamber sheet. Thus, the ink chamber and the nozzle are connected more precisely.